Memory Performance difference between - 16GB 2Rx4 PC3-14900L-13 & 32GB 4Rx4 PC3-14900L-13

[chuckk281]

Sanjoy had a DIMM memory question and looking for advice:

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Wanted some advice on what could be the performance difference if a DL380p Gen8 with E5-2600 v2 processor is using

1. 16GB 2Rx4 PC3-14900L-13  à 16 DIMM in 2P DL380p Gen8 (2DPC)
2. 32GB 4Rx4 PC3-14900L-13 à  16  DIMM in 2P DL380p Gen8 (2DPC)
3. 16GB 2Rx4 PC3-14900L-13  à 24  DIMM in 2P DL380p Gen8 (3DPC)
4. 32GB 4Rx4 PC3-14900L-13 à  24  DIMM in 2P DL380p Gen8 (3DPC)

Considering, DRAM Bus speed in DL380p Gen8 can be maintained at 1067MHz & Power Consumption is not a concern.

Reason Why  am asking for help to quantify the performance of DL380p Gen8 with above memory configuration is because:

Configuring DDR3 DIMM in Proliant Gen8  à According to the PDF in this url, While UDIMM, RDIMM, LRDIMM, 2DPC,3DPC makes adifferences, the document also makes a statement as below

Standard DDR3 DIMMs operate at 1.5V, compared to 1.8V for DDR-2 DIMMs. DDR3 Low Voltage DIMMs operate at 1.35V. For HP ProLiant Gen8 servers, the majority of new DDR3 DIMMs are Low Voltage. These HP Smart Memory DIMMs enable the same performance as standard 1.5V DIMMs while using up to 20% less power.

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Reply from Lidia:

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Your question is a little confusing because it looks like you are concerned about the DIMM power usage (quote from configuration guide below) but want to understand performance differences.

Is the customer application latency sensitive (i.e. the read hit latency makes is important but since the bus utilization is not high, BW is not a concern) or BW sensitive (the application creates a high memory bus utilization and requires high BW to achieve best performance)?

The 16GB are R-DIMMs and will provide the lowest latency at the lowest power (they have ½ the number of DRAM devices compared with the 32GB DIMMs). Since they are ½ the capacity, if the customer application is OLTP-like and requires holding a lot of data in memory, the 16GB DIMMs will have lower performance than the 32GB DIMMs. The performance loss associated with only having ½ the memory capacity is highly dependent of the customer application.

The 32GB LR-DIMMs are 2x the capacity and higher power, they will perform better for OLTP application because they can double the memory capacity per system. They are LR-DIMMs and will have slightly higher latency than the 16GB R-DIMMs.

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